Series-parallel assemblies of diodes, such as that represented in FIG. 1, are encountered especially in certain UHF antenna steering lenses used to produce electronic scanning in space. These lenses comprise a juxtaposition of phase-shift channels each enclosing, between two metal plates parallel to the direction of propagation of the beam, a stack of elongated strips which are arranged parallel to the wave front of the beam and which are each constituted by a printed circuit card supporting a network of conducting wires arranged in a ladder with rungs parallel to the direction of the electric field. The rungs are divided into two pieces linked by diodes which make it possible, on demand, to render them continuous or interrupted from the electrical point of view. This modifies their impedances and, consequently, the phase shift which the incident UHF wave undergoes. The various phase-shift combinations which it is possible to make the UHF wave undergo in its passage through the phase-shift channels make it possible to deflect the UHF beam, on demand, in various directions in order to produce scanning in space.
In order to prevent the short-circuiting of one diode disturbing the operation of all the other diodes of a strip, the interconnecting wires arranged along the uprights of the ladder are divided up. This leads to a distribution of the diodes into several groups within which they are connected in parallel in the same direction, the groups being themselves connected together in series in the same direction.
For more details on these strips and their assemblies of diodes within a UHF antenna steering lens, reference may be had to the French Patent FR-A-2,469,808.
In order to test the correct operation of the diodes of a strip, it is possible to supply the whole of the assembly from a chopping current generator and to check the presence of the current in each diode by moving the strip under a current measuring probe. However, at the UHF wavelengths envisaged, the short lengths of the connecting wires of the diodes which constitute the rungs of the ladder do not make for easy distinction between the currents flowing in the diodes and those flowing in the interconnecting wires constituting the rungs of the ladder.
Furthermore, the duration of the test is relatively long by reason of the time necessary for moving the strip and causing the diodes to come one by one under the current measuring probe.
The solution which consists in using as many current measuring probes as diodes, is unacceptable by reason of the high cost price of a current measuring probe.